The present invention relates to a structure of an exhaust gas turbine supercharger, and more particularly, to a structure for supporting a turbine nozzle in an exhaust gas turbine supercharger.
Heretofore known representative superchargers adapted to be equipped on a diesel engine are illustrated in cross-section in FIGS. 1 and 2. The supercharger shown in FIG. 1 is called an outside bearing type supercharger because its journal bearings 9 and 10 are disposed outside (at the opposite ends) of turbine drive blades 3 and an impeller 6 of a blower. On the other hand, the supercharger shown in FIG. 2 is called an inside bearing type supercharger because its journal bearings 9 and 10 are disposed inside of turbine blades 3 and an impeller 6 of a blower.
In operation of the supercharger, as is well-known in the art, an exhaust gas from a diesel engine enters into the supercharger through a gas inlet casing 1, and the heat energy of the exhaust gas is converted into kinetic energy by means of a turbine nozzle 2 to apply a torque to turbine blades 3. The exhaust gas discharged from the turbine blades 3 is passed through a gas outlet casing 4 and is exhausted via a stack. A rotor shaft 5 driven by the turbine blades 3 drives an impeller 6 mounted at the other end of the rotor shaft 5. Owing to the rotation of the impeller 6, air is sucked through an intake casing 11, is pressurized during passage through the impeller 6, is further raised in pressure by a diffuser 7, and is fed to a diesel engine through a blower casing 8.
One of the problems which arise during normal use of such superchargers is blocking of the exhaust gas passageway and lowering of the turbine performance which may be caused by a substance or scales adhering to the turbine nozzle 2 and the turbine blades 3. Since the turbine blades 3 are rotating generally at a very high speed, the adhesion of scale thereto is not greatly significant. However, adhesion of scale to the turbine nozzle 2 does cause a problem. This scale flows into the supercharger together with the exhaust gas from the main diesel engine, and it consists of unburned carbon and inorganic salts. The scale normally adheres very rigidly and cannot be readily removed. In order to perfectly remove the scale adhered onto the turbine nozzle 2, the turbine nozzle 2 must be dismantled from the supercharger and then the scale is removed from the nozzle (as by a wire brush after boiling).
The disadvantage of prior art superchargers is that the dismantling operation of the turbine nozzle was very troublesome.
More particularly, in the case of the outside bearing type supercharger illustrated in FIG. 1, in order to dismantle the turbine nozzle 2, the gas inlet casing 1 must be removed. For removing the gas inlet casing 1, the coupling bolts between the exhaust pipe of the main diesel engine and the gas inlet casing 1, as well as the bolts 12, must be removed, and also upon extracting the casing 1 the rotor shaft 5 must be supported so that it will not fall down. Although the turbine nozzle 2 can be dismantled through the above-mentioned process from a theoretical basis, normally the bolts on the exhaust gas side are not removable because of seizure, so that in practice the intake casing 11 is at first removed, and after the casings have been dismantled successively from the blower side and the rotor shaft 5 has been extracted from the blower side, the nozzle fixing bolts 13 are removed and then the turbine nozzle 2 is taken out. In any case, such a dismantling operation becomes a large-scaled operation.
Likewise, in order to dismantle the turbine nozzle 2 in the inside bearing type supercharger illustrated in FIG. 2, after the intake casing 11 has been removed and the casings on the blower side have been removed, the impeller 6 is dismantled. After the journal bearings 9 and 10 have been removed, a gas outlet casing cover 21 is removed and then the rotor shaft 5 is extracted to the exhaust gas side. Subsequently, bolts 23 are removed and the turbine nozzle 2 is taken out.
Though it is desirable to frequently clean the turbine nozzle 2, due to the fact that the operation of dismantling the turbine nozzle 2 is troublesome and laborious as described above, normally it is not dismantled for a period of about one year. During such period, the efficiency of the turbine is lowered and the amount of air supplied to the main diesel engine is reduced. Consequently, adverse effects such as, for example, a rise in the exhaust gas temperature are affected upon the main diesel engine.
On the other hand, under the world wide tendency for energy savings, the nature of the fuel oil for the main diesel engine is increasingly degraded, combustion residuals flow more and more into the supercharger jointly with the exhaust gas, and thereby the tendency of adhesion and accumulation of the residuals on the turbine nozzle is increasing. Under such circumstances, the requirement for the laborious work as described above upon dismantling of the turbine nozzle presents a substantial problem to the user of a diesel engine.